Ketogenic diet and ketone bodies enhance the anticancer effects of PD-1 blockade.

Limited experimental evidence bridges nutrition and cancer immunosurveillance. Here, we show that ketogenic diet (KD) - or its principal ketone body, 3-hydroxybutyrate (3HB), most specifically in intermittent scheduling - induced T cell-dependent tumor growth retardation of aggressive tumor models. In conditions in which anti-PD-1 alone or in combination with anti-CTLA-4 failed to reduce tumor growth in mice receiving a standard diet, KD, or oral supplementation of 3HB reestablished therapeutic responses. Supplementation of KD with sucrose (which breaks ketogenesis, abolishing 3HB production) or with a pharmacological antagonist of the 3HB receptor GPR109A abolished the antitumor effects. Mechanistically, 3HB prevented the immune checkpoint blockade-linked upregulation of PD-L1 on myeloid cells, while favoring the expansion of CXCR3+ T cells. KD induced compositional changes of the gut microbiota, with distinct species such as Eisenbergiella massiliensis commonly emerging in mice and humans subjected to carbohydrate-low diet interventions and highly correlating with serum concentrations of 3HB. Altogether, these results demonstrate that KD induces a 3HB-mediated antineoplastic effect that relies on T cell-mediated cancer immunosurveillance.

Multifaceted modes of action of the anticancer probiotic Enterococcus hirae.

A deviated repertoire of the gut microbiome predicts resistance to cancer immunotherapy. Enterococcus hirae compensated cancer-associated dysbiosis in various tumor models. However, the mechanisms by which E. hirae restored the efficacy of cyclophosphamide administered with concomitant antibiotics remain ill defined. Here, we analyzed the multifaceted modes of action of this anticancer probiotic. Firstly, E. hirae elicited emigration of thymocytes and triggered systemic and intratumoral IFNγ-producing and CD137-expressing effector memory T cell responses. Secondly, E. hirae activated the autophagy machinery in enterocytes and mediated ATG4B-dependent anticancer effects, likely as a consequence of its ability to increase local delivery of polyamines. Thirdly, E. hirae shifted the host microbiome toward a Bifidobacteria-enriched ecosystem. In contrast to the live bacterium, its pasteurized cells or membrane vesicles were devoid of anticancer properties. These pleiotropic functions allow the design of optimal immunotherapies combining E. hirae with CD137 agonistic antibodies, spermidine, or Bifidobacterium animalis. We surmise that immunological, metabolic, epithelial, and microbial modes of action of the live E. hirae cooperate to circumvent primary resistance to therapy.

Gut microbiota signatures are associated with toxicity to combined CTLA-4 and PD-1 blockade.

Treatment with combined immune checkpoint blockade (CICB) targeting CTLA-4 and PD-1 is associated with clinical benefit across tumor types, but also a high rate of immune-related adverse events. Insights into biomarkers and mechanisms of response and toxicity to CICB are needed. To address this, we profiled the blood, tumor and gut microbiome of 77 patients with advanced melanoma treated with CICB, with a high rate of any ≥grade 3 immune-related adverse events (49%) with parallel studies in pre-clinical models. Tumor-associated immune and genomic biomarkers of response to CICB were similar to those identified for ICB monotherapy, and toxicity from CICB was associated with a more diverse peripheral T-cell repertoire. Profiling of gut microbiota demonstrated a significantly higher abundance of Bacteroides intestinalis in patients with toxicity, with upregulation of mucosal IL-1ß in patient samples of colitis and in pre-clinical models. Together, these data offer potential new therapeutic angles for targeting toxicity to CICB.

Elucidating the gut microbiota composition and the bioactivity of immunostimulatory commensals for the optimization of immune checkpoint inhibitors.

Accumulating evidence from preclinical studies and human trials demonstrated the crucial role of the gut microbiota in determining the effectiveness of anticancer therapeutics such as immunogenic chemotherapy or immune checkpoint blockade. In summary, it appears that a diverse intestinal microbiota supports therapeutic anticancer responses, while a dysbiotic microbiota composition that lacks immunostimulatory bacteria or contains overabundant immunosuppressive species causes treatment failure. In this review, we explore preclinical and translational studies highlighting how eubiotic and dysbiotic microbiota composition can affect progression-free survival in cancer patients.

Cross-reactivity between tumor MHC class I-restricted antigens and an enterococcal bacteriophage.

Intestinal microbiota have been proposed to induce commensal-specific memory T cells that cross-react with tumor-associated antigens. We identified major histocompatibility complex (MHC) class I-binding epitopes in the tail length tape measure protein (TMP) of a prophage found in the genome of the bacteriophage Enterococcus hirae Mice bearing E. hirae harboring this prophage mounted a TMP-specific H-2Kb-restricted CD8+ T lymphocyte response upon immunotherapy with cyclophosphamide or anti-PD-1 antibodies. Administration of bacterial strains engineered to express the TMP epitope improved immunotherapy in mice. In renal and lung cancer patients, the presence of the enterococcal prophage in stools and expression of a TMP-cross-reactive antigen by tumors correlated with long-term benefit of PD-1 blockade therapy. In melanoma patients, T cell clones recognizing naturally processed cancer antigens that are cross-reactive with microbial peptides were detected.

Chemotherapy-induced ileal crypt apoptosis and the ileal microbiome shape immunosurveillance and prognosis of proximal colon cancer.

The prognosis of colon cancer (CC) is dictated by tumor-infiltrating lymphocytes, including follicular helper T (TFH) cells and the efficacy of chemotherapy-induced immune responses. It remains unclear whether gut microbes contribute to the elicitation of TFH cell-driven responses. Here, we show that the ileal microbiota dictates tolerogenic versus immunogenic cell death of ileal intestinal epithelial cells (IECs) and the accumulation of TFH cells in patients with CC and mice. Suppression of IEC apoptosis led to compromised chemotherapy-induced immunosurveillance against CC in mice. Protective immune responses against CC were associated with residence of Bacteroides fragilis and Erysipelotrichaceae in the ileum. In the presence of these commensals, apoptotic ileal IECs elicited PD-1+ TFH cells in an interleukin-1R1- and interleukin-12-dependent manner. The ileal microbiome governed the efficacy of chemotherapy and PD-1 blockade in CC independently of microsatellite instability. These findings demonstrate that immunogenic ileal apoptosis contributes to the prognosis of chemotherapy-treated CC.

Docosahexaenoic acid inhibits both NLRP3 inflammasome assembly and JNK-mediated mature IL-1ß secretion in 5-fluorouracil-treated MDSC: implication in cancer treatment.

Limitation of 5-fluorouracil (5-FU) anticancer efficacy is due to IL-1ß secretion by myeloid-derived suppressor cells (MDSC), according to a previous pre-clinical report. Release of mature IL-1ß is a consequence of 5-FU-mediated NLRP3 activation and subsequent caspase-1 activity in MDSC. IL-1ß sustains tumor growth recovery in 5-FU-treated mice. Docosahexaenoic acid (DHA) belongs to omega-3 fatty acid family and harbors both anticancer and anti-inflammatory properties, which could improve 5-FU chemotherapy. Here, we demonstrate that DHA inhibits 5-FU-induced IL-1ß secretion and caspase-1 activity in a MDSC cell line (MSC-2). Accordingly, we showed that DHA-enriched diet reduces circulating IL-1ß concentration and tumor recurrence in 5-FU-treated tumor-bearing mice. Treatment with 5-FU led to JNK activation through ROS production in MDSC. JNK inhibitor SP600125 as well as DHA-mediated JNK inactivation decreased IL-1ß secretion. The repression of 5-FU-induced caspase-1 activity by DHA supplementation is partially due to ß-arrestin-2-dependent inhibition of NLRP3 inflammasome activity but was independent of JNK pathway. Interestingly, we showed that DHA, through ß-arrestin-2-mediated inhibition of JNK pathway, reduces V5-tagged mature IL-1ß release induced by 5-FU, in MDSC stably overexpressing a V5-tagged mature IL-1ß form. Finally, we found a negative correlation between DHA content in plasma and the induction of caspase-1 activity in HLA-DR- CD33+ CD15+ MDSC of patients treated with 5-FU-based chemotherapy, strongly suggesting that our data are clinical relevant. Together, these data provide new insights on the regulation of IL-1ß secretion by DHA and on its potential benefit in 5-FU-based chemotherapy.

TNFR2/BIRC3-TRAF1 signaling pathway as a novel NK cell immune checkpoint in cancer.

Natural Killer (NK) cells control metastatic dissemination of murine tumors and are an important prognostic factor in several human malignancies. However, tumor cells hijack many of the NK cell functional features compromising their tumoricidal activity. Here, we show a deleterious role of the TNFα/TNFR2/BIRC3/TRAF1 signaling cascade in NK cells from the tumor microenvironment (TME). TNFα induces BIRC3/cIAP2 transcripts and reduces NKp46/NCR1 transcription and surface expression on NK cells, promoting metastases dissemination in mice and poor prognosis in GIST patients. NKp30 engagement, by promoting the release of TNFα, also contributes to BIRC3 upregulation, and more so in patients expressing predominantly NKp30C isoforms. These findings reveal that in the absence of IL-12 or a Th1-geared TME, TNFα can be considered as a negative regulatory cytokine for innate effectors.

Gut microbiome influences efficacy of PD-1-based immunotherapy against epithelial tumors.

Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 axis induce sustained clinical responses in a sizable minority of cancer patients. We found that primary resistance to ICIs can be attributed to abnormal gut microbiome composition. Antibiotics inhibited the clinical benefit of ICIs in patients with advanced cancer. Fecal microbiota transplantation (FMT) from cancer patients who responded to ICIs into germ-free or antibiotic-treated mice ameliorated the antitumor effects of PD-1 blockade, whereas FMT from nonresponding patients failed to do so. Metagenomics of patient stool samples at diagnosis revealed correlations between clinical responses to ICIs and the relative abundance of Akkermansia muciniphila Oral supplementation with A. muciniphila after FMT with nonresponder feces restored the efficacy of PD-1 blockade in an interleukin-12-dependent manner by increasing the recruitment of CCR9+CXCR3+CD4+ T lymphocytes into mouse tumor beds.

Protective effects of polyphenol-rich infusions from carob (Ceratonia siliqua) leaves and cladodes of Opuntia ficus-indica against inflammation associated with diet-induced obesity and DSS-induced colitis in Swiss mice.

In the present study, we have investigated the effects of polyphenol-rich infusions from carob leaves and OFI-cladodes on inflammation associated with obesity and dextran sulfate sodium (DSS)-induced ulcerative colitis in Swiss mice. In vitro studies revealed that aqueous extracts of carob leaves and OFI-cladodes exhibited anti-inflammatory properties marked by the inhibition of IL-6, TNF-α and nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells concomitant with NF-κß nucleus translocation inhibition. For in vivo investigations, Swiss male mice were subjected to control or high fat diet (HFD). At the 8th week after the start of study, animals received or not 1% infusion of either carob leaves or OFI-cladode for 4 weeks and were subjected to 2% DSS administration in drinking water over last 7 days. After sacrifice, pro-inflammatory cytokines levels in plasma and their mRNA expression in different organs were determined. Results showed that carob leaf and OFI-cladode infusions reduced inflammation severity associated with HFD-induced obesity and DSS-induced acute colitis indicated by decrease in pro-inflammatory cytokines expression (as such TNF-α, IL1b and IL-6) in colon, adipose tissue and spleen. In addition, plasma levels of IL-6 and TNF-α were also curtailed in response to infusions treatment. Thus, carob leaf and OFI-cladode infusions prevented intestinal permeability through the restoration of tight junction proteins (Zo1, occludins) and immune homeostasis. Hence, the anti-inflammatory effect of carob leaves and OFI-cladodes could be attributed to their polyphenols which might alleviate inflammation severity associated with obesity and colitis.